When binary logging is enabled and
CURRENT_USER() or
CURRENT_USER is used as
the definer in any of these statements, MySQL Server ensures
that the statement is applied to the same user on both the
master and the slave when the statement is replicated. In some
cases, such as statements that change passwords, the function
reference is expanded before it is written to the binary log, so
that the statement includes the user name. For all other cases,
the name of the current user on the master is replicated to the
slave as metadata, and the slave applies the statement to the
current user named in the metadata, rather than to the current
user on the slave.